Kleptoprotein

A kleptoprotein is a protein which is not encoded in the genome of the organism which uses it, but instead is obtained through diet from a prey organism. Importantly, a kleptoprotein must maintain its function and be mostly or entirely undigested, drawing a distinction from proteins that are digested for nutrition, which become destroyed and non-functional in the process.

The bioluminescent fish Parapriacanthus ransonneti, which obtains its luciferase protein from its diet, rather than encoding it within its own genome

This phenomena was first reported in the bioluminescent fish Parapriacanthus, which has specialized light organs adapted towards counter-illumination, but obtains the luciferase enzyme within these organs from bioluminescent ostracods, including Cypridina noctiluca or Vargula hilgendorfii.[1]